From 35ce86165095543a2244b14251ca21bd5b67d824 Mon Sep 17 00:00:00 2001
From: Aliaksandr <grubian2@gmail.com>
Date: Fri, 1 May 2026 03:56:57 +0300
Subject: [PATCH] ghcWithPackages: throw on non-derivation inputs

Previously the user-supplied package list was passed directly through
`lib.closePropagation` and an `isHaskellLibrary`-attribute filter, so
mistakes such as `[ dontCheck hp.foo ]` (forgetting parentheses around
the override) silently produced a GHC environment with the affected
package missing instead of failing.

Validate each top-level entry up front. We deliberately accept any
derivation (not just Haskell libraries), because shellFor passes
mixed inputs like `libraryFrameworkDepends` through here on Darwin;
those are still silently dropped by the existing closure-side filter.
The user-error case the issue is about -- non-derivation values like
functions or strings -- is now rejected with a helpful message that
points at the canonical fix.

Fixes #30304

Assisted-by: claude-code with claude-opus-4-8[1m]-high
---
 .../haskell-modules/with-packages-wrapper.nix | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/haskell-modules/with-packages-wrapper.nix b/pkgs/development/haskell-modules/with-packages-wrapper.nix
index 9968ea355363..37bf1e450314 100644
--- a/pkgs/development/haskell-modules/with-packages-wrapper.nix
+++ b/pkgs/development/haskell-modules/with-packages-wrapper.nix
@@ -48,7 +48,24 @@ let
 
   hoogleWithPackages' = if withHoogle then hoogleWithPackages selectPackages else null;
 
-  packages = selectPackages haskellPackages ++ [ hoogleWithPackages' ];
+  # Catches obviously-wrong inputs (functions, strings, etc.) but lets
+  # non-Haskell derivations through; shellFor passes libraryFrameworkDepends
+  # and similar mixed inputs in, and those are dropped later by the
+  # closure-side `isHaskellLibrary` filter.
+  checkPackage =
+    p:
+    if p == null || lib.isDerivation p then
+      p
+    else
+      throw ''
+        ghcWithPackages: expected a derivation, got a ${builtins.typeOf p}.
+        A common cause is missing parentheses around an override, e.g.
+          (hp: [ dontCheck hp.foo ])
+        should be written as
+          (hp: [ (dontCheck hp.foo) ]).
+      '';
+
+  packages = map checkPackage (selectPackages haskellPackages ++ [ hoogleWithPackages' ]);
 
   isHaLVM = ghc.isHaLVM or false;
   ghcCommand' = "ghc";